1. Field of the Invention
The present invention relates to a revolving-ladle turret for use in plants for the continuous casting of molten steel. More particularly, the invention relates to ladles of the type having a turret member supported by a base structure with respect to which the turret member is vertically moveable, a platform supported by the turret member so that it may rotate around a vertical axis, at least two ladle-carrying arms which extend out from positions which are diametrically opposite on the platform, motor elements for rotating the platform, and motor elements for controlling the vertical movements of the turret member and of the platfor supported by it.
2. Description of the Art
It is known that by means of a turret of the above-mentioned type it has become possible to halve or at least reduce by a substantial amount the down time between two successive feeds of molten steel into the distributor of a continuous casting plant. Actually, while a first ladle, held in the casting position, unloads steel into the distributor, a second ladle full of molten steel can be loaded on the other ladle-carrying arm. At the end of these operations, the turret and the respectively empty and full ladles are raised, rotated by 180 degrees and then lowered to the beginning height to initiate the simultaneous operations of unloading molten metal from the full ladle and substitution of the empty ladle with anothe which has been previously filled.
during each of the above-mentioned movements the ladle-carrying arms must remain horizontal.
Satisfaction of this necessity is very difficult to achieve due to the constant and evident situation in which there are unbalanced loads which act on the turret. In fact, the ladles carried at the ends of the turret arms have large, different, and quite variable weights depending on the operating phase of the turret at any one time. This means that the resultant force of the loads which act on the turret not only does not coincide ever with the axis of the turret itself, but its distance from this axis varies between two limiting positions which occur when a full ladle is located to have its contents emptied and after the contents of the ladle have been emptied.
Exactly when the resultant force of the loads is in one of these two limiting positions, the vertical movement operations of the turret are carried out by the appropriate motor elements. These elements are generally comprised of two hydraulic cylinders which are symmetrically arranged with respect to the vertical axis of the turret. Since the resultant of the thrust of these cylinders coincides with the vertical axis of rotation while the resultant of the loads is in one of the two limiting positions, an unbalancing torque works against the turret during the vertical movements of the turret and must be effective resisted, or, better, eliminated.
For this purpose, changes have been proposed for affecting the hydraulic cylinders for raising and supporting the turret so that the action line of the resultant of their thrusts would be moved, from time to time, in order to coincide with the action line of the resultant of the unbalanced loads weighing on the turret.
Thus, devices and mechanisms, for example, have been devised to appropriately regulate the pressures of the operating fluids in the cylinders. Also, devices have been devised for balancing and/or compensating which, besides their recognized unreliability, have presented the inconvenience of being very complex from both the structural and functional points of view.